[mapserver-users] Shapefile spatial index challenge

[Fawcett, David (MNIT)]

I have seen examples where for the purpose of overlay operations, someone chops up their large polys into smaller ones, each with an attribute that contains the id for the large poly.  I don’t know if that would fit your use case.

David.

From: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Ben Madin
Sent: Friday, October 23, 2015 1:23 AM
To: Lydon Chandra
Cc: mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] Shapefile spatial index challenge

G’day Lydon,

I feel your pain, but there is little benefit to creating more quadrants. The idea (as I understand it - could be wrong) is to be able to use a (fast) bounding box to find the polygons to test, rather than having to test against every polygon using more complex algorithms.

I suppose you could consider that if you want to find out if a point is in one or more of your polygons, the benefit of having more index squares. You only have 8 polygons (I presume) so this should limit you in most cases to only having to compare your ‘point’ with only a couple of polygons using the more complex algorithms.

hth

cheers

Ben




On 2015-10-08, at 21:31 , Lydon Chandra <lydon_chandra at technologyonecorp.com<mailto:lydon_chandra at technologyonecorp.com>> wrote:

Hi List,

How can we generate more quadrants for the spatial index for the Australia polygon below ?

Using MapServer shptree, even forcing it to go to 50 level deep, the spatial index does not have more quadrants.

More data and details at:
http://www.evernote.com/l/AhrYASBGtqVOkJn0BLqZkceADvOsA_UBfvY/


<image.png>


Kind Regards,
Don




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